The Government has lost a vote on Seanad reform after three Labour Senators defied their party whip.
They voted in support of a motion calling on the issue to be considered by the forthcoming Constitutional Convention.
Denis Landy, James Heffernan and John Kelly backed the Opposition measure after a debate to which Government senators did not contribute.
The motion had been allowed earlier after the Government failed to muster the numbers to block it.
The debate was marked by spirited contributions from Fianna Fáil and independent Senators, who accused the Government of muzzling its own members.
Fianna Fáil’s Ned O'Sullivan said the atmosphere was reminiscent of the last days of Grattan's parliament, while Marc McSharry accused the Government of stifling democracy.
Independent Senator David Norris said ministers were guilty of gross hypocrisy in their attitude to the Seanad.
The Government was forced into holding a two-hour debate on the future of the Seanad after it twice lost a vote in the Upper House this morning.
The Government plans a referendum on the abolition of the Upper House next year, and has said the Convention will not discuss this proposal.